The invention relates to a buckling control system for steerable articulated vehicles, especially articulated busses. Such vehicles include a forward steerable wagon or vehicular section and at least one following wagon or vehicular section connected thereto by a pivotal connection. The buckling control system includes devices effective to forceably counteract enlargements and also reductions in the buckling angle between the vehicular sections. A computer control system is provided which either
(i) determines an adjustable desired value or desired value range for a buckling angle corresponding to extensively skid-free vehicle drive, this determination being made in dependence upon the actual turning angle of the forward vehicular section and the preceeding travel path of the vehicle, with the control device being operated to apply counter forces against further increases in the buckling angle during increasing deviations between the actual value of the buckling angle and the determined desired angle/desired angle region of the buckling angle;
or
(ii) determines a maximum value of the buckling angle based upon the turning angle corresponding to an essentially skid-free drive corresponding to essentially pure circular drive at that angle, and applying buckling angle control forces against tendencies to exceed this determined maximum buckling angle.
A control system corresponding to the first above mentioned alternative control arrangement is described in a not published German patent application P No. 32 30 617.2. This arrangement has the advantage that the deviations between the actual value and the desired value of the buckling angle as a rule can be held in a relatively narrow range which through corresponding control of the hinge blocking arrangement only permits such buckling angle changes which bring about an approach of the actual value and the desired value. However, if the driver turns the steering system too sharply, for the vehicle driving speed with a resultant excessive turning angle that no longer permits skid-free drive, the computer control hinge blocking mechanism will seek to have the actual value of the buckling angle approach the desired value, a condition which will then make the already critical driving condition even more dangerous. Namely, the computer calculates by increasing turning angle an increasing desired value of the buckling angle so that finally an unsuitably strong buckling is permitted.
An arrangement corresponding to the second above-mentioned alternative control system is shown in German published examined application (DE-AS) No. 24 20 203. In this type of arrangement, the permitted buckling angle for the control arrangement is only limited at a value which corresponds to an essentially skid-free pure circular travel path of the vehicle at the given turning angle of the forward vehicular section and the given velocity. However, here also the control system permits too much buckling of the vehicle under certain circumstances if the steering linkage is too rapidly turned considering the vehicle velocity and a corresponding further skid-free drive is no longer resultant.
This problem was not really recognized prior to the present invention. Also the following cited publications give no hint of this problem or the solution thereof.
From German published unexamined application (DE-OS) No. 29 35 437 it is only shown that, with a slippery road path, the increase in the buckling angle above a certain predetermined value based upon the selected turning angle should be prevented and centrifigal movements as well as oscillating motions of the following wagon or vehicular section should be damped in each driving condition to a tolerable level.
In German published unexamined application (DE-OS) No. 30 04 409 there is proposed a velocity dependent damping of the buckling angle changes, so that certainly the buckling angle change of velocity is reduced, without however immediately influencing the maximum value of the buckling angle.
In view of the above-indicated state of the technology, it is an object of the invention to create a buckling control system which also improves the controllability of an articulated vehicle in the cases when the driver, for example as a panic reaction, turns the steering system excessively fast.
These problems are thereby solved by the invention in that the computer control system determines velocity dependent buckling angle limiting values which can be adjusted for maximum buckling angle still assuring essentially skid-free travel and the hinged or buckling connection is controlled in such a manner that forces are applied against the exceeding of this buckling angle limited value.
The invention is based upon the general concept of limiting the buckling angle below velocity dependent limiting values. This is done independently of which turning angle and which travel path dependent desired values, respectively which turning angle dependent maximum values of the buckling angle, are calculated without considering whether with the respective turning angle and the respective velocity there is still any essentially skid-free driving condition available. Through the invention it is achieved that the buckling angle also can not increase further if the steering linkage by already excessively strong sliding is further turned.
Independently of the manner of control of the blocking control at the hinged articulated connection, it is useful to provide an arrangement for computer controlled damping units that are dependent upon the vehicle velocity and increase the damping of buckling angle changes with increasing vehicle velocity. With such arrangements, according to a preferred embodiment of the invention, it is provided that the damping for changing stable forward driving conditions, with an essentially skid-free drive through curves with changing turning and/or buckling angles, is decreased the greater the difference between the actual value of the buckling value and the maximum permitted value. In this manner it is achieved that the buckling connection can be adjusted in the respective correct direction without force. This is especially of significance for city travel when the vehicle for example, must turn around street crossings and furthermore curves with very small radii.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.